The following happened on an i.MX25 using flexcan with many packets on
the bus:
The rx-offload queue reached a length more than skb_queue_len_max. In
can_rx_offload_offload_one() the drop variable was set to true which
made the call to .mailbox_read() (here: flexcan_mailbox_read()) to
_always_ return ERR_PTR(-ENOBUFS) and drop the rx'ed CAN frame. So
can_rx_offload_offload_one() returned ERR_PTR(-ENOBUFS), too.
can_rx_offload_irq_offload_fifo() looks as follows:
| while (1) {
| skb = can_rx_offload_offload_one(offload, 0);
| if (IS_ERR(skb))
| continue;
| if (!skb)
| break;
| ...
| }
The flexcan driver wrongly always returns ERR_PTR(-ENOBUFS) if drop is
requested, even if there is no CAN frame pending. As the i.MX25 is a
single core CPU, while the rx-offload processing is active, there is
no thread to process packets from the offload queue. So the queue
doesn't get any shorter and this results is a tight loop.
Instead of always returning ERR_PTR(-ENOBUFS) if drop is requested,
return NULL if no CAN frame is pending.
Changes since v1: https://lore.kernel.org/all/20220810144536.389237-1-u.kleine-koenig@pengutronix.de
- don't break in can_rx_offload_irq_offload_fifo() in case of an error,
return NULL in flexcan_mailbox_read() in case of no pending CAN frame
instead
Fixes: 4e9c9484b0 ("can: rx-offload: Prepare for CAN FD support")
Link: https://lore.kernel.org/all/20220811094254.1864367-1-mkl@pengutronix.de
Cc: stable@vger.kernel.org # v5.5
Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Tested-by: Thorsten Scherer <t.scherer@eckelmann.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Most flexcan IP cores support 2 RX modes:
- FIFO
- mailbox
The flexcan IP core on the MCF5441X cannot receive CAN RTR messages
via mailboxes. However the mailbox mode is more performant. The commit
| 1c45f5778a ("can: flexcan: add ethtool support to change rx-rtr setting during runtime")
added support to switch from FIFO to mailbox mode on these cores.
After testing the mailbox mode on the MCF5441X by Angelo Dureghello,
this patch marks it (without RTR capability) as supported. Further the
IP core overview table is updated, that RTR reception via mailboxes is
not supported.
Link: https://lore.kernel.org/all/20220121084425.3141218-1-mkl@pengutronix.de
Tested-by: Angelo Dureghello <angelo@kernel-space.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This patch adds a private flag to the flexcan driver to switch the
"rx-rtr" setting on and off.
"rx-rtr" on - Receive RTR frames. (default)
The CAN controller can and will receive RTR frames.
On some IP cores the controller cannot receive RTR
frames in the more performant "RX mailbox" mode and
will use "RX FIFO" mode instead.
"rx-rtr" off - Waive ability to receive RTR frames. (not supported on all IP cores)
This mode activates the "RX mailbox mode" for better
performance, on some IP cores RTR frames cannot be
received anymore.
The "RX FIFO" mode uses a FIFO with a depth of 6 CAN frames.
The "RX mailbox" mode uses up to 62 mailboxes.
Link: https://lore.kernel.org/all/20220107193105.1699523-6-mkl@pengutronix.de
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Co-developed-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Most flexcan IP cores support 2 RX modes:
- FIFO
- mailbox
Some IP core versions cannot receive CAN RTR messages via mailboxes.
This patch adds quirks to document this.
This information will be used in a later patch to switch from FIFO to
more performant mailbox mode at the expense of losing the ability to
receive RTR messages. This trade off is beneficial in certain use
cases.
Link: https://lore.kernel.org/all/20220107193105.1699523-5-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Most flexcan IP cores support 2 RX modes:
- FIFO
- mailbox
The names for these modes were chosen to reflect the name of the
rx-offload mode they are using.
The name of the RX modes should better reflect their difference with
regards the flexcan IP core. So this patch renames the various
occurrences of OFF_FIFO to RX_FIFO and OFF_TIMESTAMP to RX_MAILBOX:
| FLEXCAN_TX_MB_RESERVED_OFF_FIFO -> FLEXCAN_TX_MB_RESERVED_RX_FIFO
| FLEXCAN_TX_MB_RESERVED_OFF_TIMESTAMP -> FLEXCAN_TX_MB_RESERVED_RX_MAILBOX
| FLEXCAN_QUIRK_USE_OFF_TIMESTAMP -> FLEXCAN_QUIRK_USE_RX_MAILBOX
Link: https://lore.kernel.org/all/20220107193105.1699523-4-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
